21351202440 has 128 divisors (see below), whose sum is σ = 66686112000. Its totient is φ = 5462166528.

The previous prime is 21351202403. The next prime is 21351202451. The reversal of 21351202440 is 4420215312.

It is a Harshad number since it is a multiple of its sum of digits (24).

It is a self number, because there is not a number n which added to its sum of digits gives 21351202440.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 526821 + ... + 565899.

It is an arithmetic number, because the mean of its divisors is an integer number (520985250).

Almost surely, 2^21351202440 is an apocalyptic number.

21351202440 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21351202440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33343056000).

21351202440 is an abundant number, since it is smaller than the sum of its proper divisors (45334909560).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21351202440 is a wasteful number, since it uses less digits than its factorization.

21351202440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 39279 (or 39275 counting only the distinct ones).

The product of its (nonzero) digits is 1920, while the sum is 24.

Adding to 21351202440 its reverse (4420215312), we get a palindrome (25771417752).

The spelling of 21351202440 in words is "twenty-one billion, three hundred fifty-one million, two hundred two thousand, four hundred forty".